As an iPhone player, I think they hit it just right with the rollout of the new buy-brutes feature. During the sale period (they lowered the price to $1) there was a big boom in new players, and then when it ended, the new players tailed off gradually to almost nothing. No new people were buying the game, no existing players were getting new pupils, and a small number of elite players had locked up thousands of pupils, preventing most other players from unlocking the full game.
Then they released the store -- instantly, no one needed to recruit new players in order to gain pupils, because their existing pupils would buy brutes and fill up their dojos. You can now buy huge blocks of fights and boost all your brutes' levels, thereby boosting your master's levels as well. It no longer matters that elite players have locked up so many pupils, or that nobody is buying the game. Bulkypix can now get far more money from their existing players than they would have been able to get by selling new copies of the game. This wouldn't have worked if they had done it earlier, because they needed the recruitment to build their market. It wouldn't have worked if they'd done it later because too many existing players would quit out of frustration. Instead, they built their market up to a peak and then monetized it, changing from an outside sales model to an inside one. As long as they keep rolling out new products to keep their market buying, they never have to sell another copy of the game.